Saves roughly 20% off living/Life(), makes gravity event based (#74084)

## About The Pull Request

Right now, each time life processes we need to run has_gravity, and
check its output against a bunch of thresholds.
We could save off that second bit by caching the previous value, but
we'd still be only updating this every 2 seconds.

This potentially delayed updating leads to really janky feeling behavior
around transition points too (like when moving on/off the sand on tram
station)

So instead of doing this updating off life(), let's make it event based.
We'll decompose has_gravity, and take all the values it relies on, and
check for them changing ourselves.
That way we get instant response, and can save all the wasted
has_gravity calls.

This constant checking on movement adds a few signal registrations, a
connect_loc, and some logic on living/Moved

The Moved logic increases Moved's self by 50%, roughly 1 second a round
at worst.
Don't have concrete numbers for the connect_loc

(new self / old self)

![image](https://user-images.githubusercontent.com/58055496/226091990-8cbeef82-6a37-488c-a0b6-cf570156c2dc.png)

In constrast, handle_gravity is currently on average maybe 15 seconds.


![image](https://user-images.githubusercontent.com/58055496/226092056-5fc7fc59-46e2-4e01-a6ee-6867de30c1f0.png)

I could JUST save maybe 13 seconds and not spend the 1 by storing the
previous gravity value, but I think this is worth the ux changes. It
does add some extra resistance to change, but s much nice.

Moved some functions around too, and removed now redundant
update_gravity calls

## Why It's Good For The Game

Snappier gravity, faster Life()

## Changelog
🆑
qol: Human gravity will react to changes instantly, instead of waiting
for the next process tick. Hopefully this feels better and not worse
/🆑

code/modules/mod/modules/modules_maint.dm

@@ -287,7 +287,6 @@
 	playsound(src, 'sound/effects/curseattack.ogg', 50)
 	mod.wearer.AddElement(/datum/element/forced_gravity, NEGATIVE_GRAVITY)
 	RegisterSignal(mod.wearer, COMSIG_MOVABLE_MOVED, PROC_REF(check_upstairs))
-	mod.wearer.update_gravity(mod.wearer.has_gravity())
 	ADD_TRAIT(mod.wearer, TRAIT_SILENT_FOOTSTEPS, MOD_TRAIT)
 	check_upstairs() //todo at some point flip your screen around
 
@@ -303,7 +302,6 @@
 	qdel(mod.wearer.RemoveElement(/datum/element/forced_gravity, NEGATIVE_GRAVITY))
 	UnregisterSignal(mod.wearer, COMSIG_MOVABLE_MOVED)
 	step_count = 0
-	mod.wearer.update_gravity(mod.wearer.has_gravity())
 	REMOVE_TRAIT(mod.wearer, TRAIT_SILENT_FOOTSTEPS, MOD_TRAIT)
 	var/turf/open/openspace/current_turf = get_turf(mod.wearer)
 	if(istype(current_turf))

code/modules/mod/modules/modules_science.dm

@@ -74,7 +74,6 @@
 	if(mod.wearer.has_gravity())
 		new /obj/effect/temp_visual/mook_dust(get_turf(src))
 	mod.wearer.AddElement(/datum/element/forced_gravity, 0)
-	mod.wearer.update_gravity(mod.wearer.has_gravity())
 	playsound(src, 'sound/effects/gravhit.ogg', 50)
 
 /obj/item/mod/module/anomaly_locked/antigrav/on_deactivation(display_message = TRUE, deleting = FALSE)
@@ -82,7 +81,6 @@
 	if(!.)
 		return
 	mod.wearer.RemoveElement(/datum/element/forced_gravity, 0)
-	mod.wearer.update_gravity(mod.wearer.has_gravity())
 	if(deleting)
 		return
 	if(mod.wearer.has_gravity())